His rookie season with the Philadelphia Phillies was in 2006 when he made 23 starts, and since then, has piled up 343 starts and 2,247 innings on his lanky left arm. He's now 33 years old, slinging it for the Rangers after being acquired in a midseason deal with the Phils back in 2015.

The 2017 season has been a bit of a weird one for Hamels. He has yet to give up more than three earned runs in any of his five starts, including his last outing on Wednesday, which included 6.2 innings of work and just 3 earned runs allowed on 7 hits in the Rangers' 14-3 win over the Minnesota Twins.

Most of his starts this year have been like that. By the end of the game, the results are good, but lying underneath are some peripherals that indicate regression may be coming.

Either that, or it's another example of a weird April sample size.

In Wednesday's start, Hamels struck out just one hitter, which isn't a new trend. He hasn't struck out more than five hitters in a single start, and has retired opposing batters on strikes fewer than four times on three different occasions. That's surprisingly low for a hurler who is used to generating a lot of swings and misses.

Here are how some of his numbers stack up this year with previous seasons. Take note of the steep drop-off in his strikeout percentage (K%), strikeouts per nine innings (K/9), Fielding Independent Pitching (FIP) and skill independent ERA (SIERA).

Season

BB%

K%

K/9

ERA

FIP

SIERA

2017

9.2%

11.5%

4.13

3.03

5.11

5.24

2016

9.1%

23.6%

8.97

3.32

3.98

3.99

Career

6.6%

23.2%

8.56

3.31

3.55

3.48

This chart by Brooks Baseball graphs his whiff rate among all his pitches.

The drop off is most notable when you look at his most effective pitch, the changeup. Hamels is also using his pitches a little differently this season, which is displayed below.

Season

FB%

CT%

CB%

CH%

2017

51.9%

17.2%

10.5%

20.3%

2016

43.7%

23.0%

14.6%

18.6%

Career

51.4%

12.0%

10.6%

25.9%

Compared to last year, Hamels is throwing way more fastballs and a few more changeups while utilizing his cutter and curveball much less. And while his 2017 numbers look more in line with what he's done throughout his career, it's important to remember that his fastball percentage was much higher at the start of his career before developing a cut fastball in 2010.

The table below shows that hitters are chasing fewer pitches (O-Swing%) and are zeroing in more on pitches in the zone (Z-Swing%). Hitters are making far more contact against him this season, as noted by his contact percentage (Contact%) and swinging-strike percentage (SwStr%). He's also generating much less softly contact (Soft%) this year, while his hard-hit rate (Hard%) is on the rise.

Season

O-Swing%

Z-Swing%

Contact%

SwStr%

Soft%

Hard%

2017

25.1%

71.2%

82.8%

7.5%

14.0%

36.0%

2016

35.0%

68.0%

60.9%

12.2%

20.4%

32.0%

Career

32.0%

68.5%

75.0%

12.3%

20.7%

28.0%

One other thing to note is a slight drop in velocity. His fastball is currently averaging 91.8 mph, which is a little slower than last year's 92.6 mph. His curveball and changeup are also all down by about the same amount, according to FanGraphs.

Is this just a fluky early-season blip that will correct itself over the coming months? Is there a mechanical flaw that needs to be corrected? Or is it a sign that Hamels' long career is catching up with him?

We'll know more as the year progresses, but his peripherals indicate he's performed a bit better than he should have so far. And unless things change, that ERA is likely to start creeping up.